Fixing a timing issue

[Evanm21]

Hey all,

 

I'm encountering an issue of backfire through the carburetor. It spits gasoline back up through the carb and sometimes fireballs. I was thinking maybe the intake and exhaust ports were flip flopped? I'm at a loss right now.

 

Originally, i had overheating issues due to a blown head gasket and water was mixing with the oil. In preparation for repairing the head gasket, i did some research online and tutorial videos to learn the things i needed to mark. However, i made the mistake of not marking my cam sprocket before i pulled it out. I had looked at the timing notch and had aligned it with the timing notch on the cam tower. I had taken a picture of that to ensure i could place it back. Two days later, after work getting in the way of things and other more pressing projects, i had returned to the Datsun and replaced everything based off the picture i had taken. 

 

One weird thing i noticed though was, the sprocket did not want to fit onto the camshaft as easily as it was removed. The camshaft had moved a little bit but i was able to realign it with the timing notch on the cam tower. I've included pictures with my work and the current set up.

 

I have the intake and exhaust at 10 and 2. Dizzy rotor is facing towards the cab of the car, in the direction of the rear most cylinder. and the timing on the crank pulley is at/close to zero. The only thing that is slightly off is the cam sprocket. Its very slightly retarded(?) in its current position.

 

Can anyone help?

 

 

[datzenmike]

Set to TDC on the compression stroke #1 by turning the crankshaft pulley with a breaker bar. #1 cam lobes should be at 10 and 2... this is just a rough marker to confirm the valves are closed, that's all. Distributor rotor should be pointing to the #1 plug wire on the cap above it just confirms everything. Turn only clockwise, do not back up to set the timing mark at zero. It's common to overshoot so if you do back up 1/4 turn and try again and again. Once you have it perfectly set at TDC  look down at the back of the cam sprocket. There is a notch and just above it on the cam thrust plate is a small horizontal mark. If properly timed the V notch should be just below it or just slightl y to the right as viewed from the front. It should look like this....

 

 

If slightly to the left, block the timing chain tensioner, pop the cam sprocket off and move to the next number. If wildly off it may be off one tooth. (MIGHT BE A GOOD IDEA TO LOOSEN THE CAM SPROCKET BOLT BEFORE SETTING TDC SO IT DOESN'T GET BUMPED) If you have an L16 it comes from the factory on the #1 hole, L20Bs and L18s are on #2. This above is the orientation you want no matter how or what you do to set it.

 

When done adjusting reset to TDC using the above method and confirm the V to line is correct. Turning only clockwise assures that ALL chain slack is on the driver's side of the engine and the cam and valve timing exactly as when the engine is running. Backing the engine will introduce slack and the cam timing will read wrong. This is why to back up 1/4 turn then turn clockwise.

[banzai510(hainz)]

So you did this with the front cover still on and trimming wedge installed?

Getting the sprocket may be harder to get back on one might have to rotate the cam clockwise to get more slack sprocket on.Tighten it up slightly.

then rotate the  motor CCW  a little then put to TDC then see where the timing lines up. If not mark the chain to hope you go in the right direction next time you adjust .if correct tighten cam up to 100 pounder 

[Evanm21]

Thanks for such quick replies! I'll be adjusting the timing sprocket tomorrow night. Strangely, when i pulled the sprocket off originally it was set to the number 3 timing hole. And i see my images didn't upload, so here are some links if you care to look. My timing mark is set to the left of the timing mark on the thrust plate. Those small degrees could be setting the timing off bad enough to spit through the carburetor?

 

And to answer your question, yes i used a chain locking wedge that i fab'd myself out of some old plywood. Is there a problem if i dont? From what I've read on this forum, dropping the chain without a wedge can create some issue with putting the sprocket back on. Is that primarily the issue that comes to light or does that affect other things?

 

https://imgshare.io/image/UGJXe
https://imgshare.io/image/UGH5w
https://imgshare.io/image/UGcL8
https://imgshare.io/image/UGTjK
https://imgshare.io/image/UGqlS

[datzenmike]

 

On the face of it... this looks advanced, however I must stress that when setting the timing mark you must turn only in a clockwise direction and stop at the mark. Aly counterclockwise movement will give an incorrect reading. If you are sure you have done this correctly then disregard.

 

Yes it normally does come from the factory on the #2 hole but the #3 is there for adjusting out any stretch (which I have never seen yet) or more likely, if the head was re surfaced. Try setting on the #2 hole. It will have better low RPM torque than if the cam is advanced like that but it won't fix the carb spitting. BTW the cam timing is unrelated to the ignition timing so adjusting one doesn't affect the other.

 

If the timing chain tensioner falls out THAT is the problem. It can't be put back in place without removing the timing cover, a job of more than a few hours.

 

Spitting/backfiring out the carb...

 

Plug wires mixed up. Should be 1,3,4,2 in a counter clockwise direction. Usually 2 and 3 are reversed.

Timing way too advanced but usually won't start, spits while trying to start.

Lean mixture from carb. Usual to backfire during cold start up without a choke.

Valve lash too tight. Or damaged valve seat, burned valve.*

 

* Check the lash anyway as valves can be harmed over time from being too tight.

 

[banzai510(hainz)]

Be honest I wish people would not be in a rush to adjust and fuck with movement of the timming chain /take heads off ect….

That is not enough off on the sprocket to make the sputtering.Just my opinion. I seen sprocket off a tooth or even 2 and still run. also make sure you do this clockwise  as you come up to Zero on crank to keep the tension on there to get your timming right

 

I would have ck the timming on the distributor, condensor, tighten of the points and adjust them  and side to side wiggle in the distributor shaft. Or YOU maybe added a Hotter coil and the points cant take it. Use only a point coil with the ballast resisitor